The present invention relates to metering systems, and, in particular, to distributed metering systems using wireless communication.
Metering is the periodic measurement of a parameter at multiple locations. For example, utility companies meter the natural gas, electricity and water consumed by households.
The collection of data from a metering system is usually performed by physical inspection of individual meters. For example, in residential areas, electrical utility companies use electromechanical meters with rotating disks to measure the consumption of electricity. Electrical utility companies send a xe2x80x9cmeter readerxe2x80x9d to record the meter measurement about once a month. Metering of natural gas and water is handled similarly.
Utility companies often wish to charge different rates at different times. For example, an electrical utility company may wish to charge higher rates during peak hours of consumption, e.g., the morning and evening. In addition, electrical utility companies may wish to apply a penalty if a consumer exceeds a certain limit within a particular period of time. Unfortunately, electromechanical meters do not permit this objective to be achieved because they show only the cumulative consumption of electricity at the time of inspection.
The general ability to provide information about the history of a parameter at the time of inspection, e.g., something other than a cumulative total, will be referred to as profiled metering. Two basic approaches have been used to provide profiled metering.
One approach involves recording the meter measurements on paper, magnetic tape or computer memory for subsequent collection by physical inspection. The other approach is to use more complex meters that include a microprocessor, a clock and a memory. The microprocessor is preprogrammed with a particular billing schedule to increment a selected register depending on an internal clock. Again, the contents of the registers are collected by physical inspection. Unfortunately, these complex meters are expensive and unreliable. In particular, after a power failure, the clock will differ from real time and an incorrect register may be incremented.
Another problem with electromechanical meters is that meter measurements need to be gathered by physical inspection by xe2x80x9cmeter readersxe2x80x9d. The physical inspection of meters by is expensive. An automated system to electronically transmit metering information could provide considerable cost savings. However, a residential community may have tens or hundreds of thousands of meters. Even with computers, the simultaneous monitoring of tens of thousands of meters by a central computer system is difficult.
In general, in one aspect, the invention provides a metering system having multiple telemetry devices and multiple collection devices. There are fewer collection devices than telemetry devices. The telemetry devices include a sensor to measure a parameter to generate measurements, a memory configured to store the measurements, and a transmitter to transmit the stored measurements to a collection device at transmission times. Each measurement is transmitted at a plurality of different transmission times. The collection devices includes a receiver to receive transmissions from the telemetry devices, a processor for extracting the measurements from the transmissions and analyzing the measurements to generate a metered function of the parameter, and a transmitter to transmit the metered function to a monitoring station.
The sensor of the metering system may include a counter to store a value, a means for incrementing the counter upon receipt of a trigger signal, and a means for storing the value from the pulse counter in the telemetry device memory and resetting the pulse counter at each measurement time. The telemetry device memory may store eighteen measurements, and may discard old measurements and store new measurements. The telemetry device may include a measurement timer for a set interval, such as 2.5 minutes, to trigger a measurement time at its expiration. A power failure may trigger a measurement. The telemetry device may store and increment a sequence counter, and detect power failures. The collection device memory may be configured to store a plurality of objects, each representing a telemetry device. Each collection device may include a means for determining and storing a time of receipt for each transmission. The metering function may be a load profile, a time-of-use profile or a demand profile. The parameter may be electrical power, fluid flow, voltage, current, temperature, pressure, or humidity.
In general, in another aspect, the invention provides a method of metering. A parameter is measured with a telemetry device to generate measurements and a plurality of measurements are stored in the telemetry device. The measurements are transmitted to a collection device at a transmission times. The measurements are extracted from the transmissions, and are analyzed to generate a metered function of the parameter. The metered function is transmitted to a monitoring station.
The advantages of the invention include the following. The metering system can provide profiled metering without physical inspection of the individual meters and uses wireless communication to transmit information. In addition, the metering system is cost-effective, reliable, resistant to power failures, and adaptable to a variety of applications.
Additional objects and advantages of the invention will be set forth in the description which follows, and in part will be obvious from the description, or may be learned by practice of the invention. The objects and advantages of the invention may be realized by means of the instrumentalities and combinations particularly pointed out in the claims.